Pseudorabies, also called Aujeszky's disease, is an acute infectious disease caused by Suid herpesvirus 1 (SuHV1) belonging to the Alphaherpesvirinae subfamily for many kinds of livestock such as swine, cattle and sheep, as well as poultry and wild animals, with the main symptoms of fever, intense itching (except swine) and encephalomyelitis. Pseudorabies in swine is found nationwide in China causing severe damages, and is one of the major diseases limiting the large-scale production of pig farms. It can result in abortion, stillborn or mummified fetuses in pregnant sows, and neurological signs, paralysis and a high death rate in piglets. Pseudorabies virus (PRV) with strong pantropic properties, neurotropic properties and latent infectivity, may establish long-term latent infection in the peripheral nervous system, and then the latently infected host starts to get sick when the latent virus is activated into the infectious virus.
According to recent research, there are reports of new features of pseudorabies, of which the significant manifestations include infection among swine at any age, horizontal transmission among swine herds, short incubation period (1˜2 days), morbidity rates between 10%˜100%, mortality rate in pigs between 10%˜100% (mortality rate in piglets can reach up to 100%), high fever in pigs after being infected (40° C.˜42° C., lasting for more than 3 days), dyspnea, diarrhea, wheezing, coughing, sneezing, hind limb paralysis, dog sitting, suddenly falling down, convulsions, lying on their sides, opisthotonus, making strokes with their forelimbs, and finally dying of exhaustion, and the infection also can cause reproductive disorder symptoms such as declined semen quality of boar, as well as abortion of pregnant sow (the abortion rate can reach up to 35%), premature birth, stillbirth, weakened piglets (weakened piglets die by 14 days of age), etc. Vaccinated pigs in prior art cannot complete resist attacks by the wild virus, and still have symptoms like high fever, depression, partially or completely loss of appetite, with an infection rate of more than 80%, a morbidity rate of more than 30% and a mortality rate between 10% and 20% (Refer to literatures in the prior art, for example, Jin-mei Peng, et al., Identification and antigenic variation of new epidemiology of pseudorabies virus from swine. Chinese Journal of Preventive Veterinary Medicine, 2013, 35(1):1-4; Wu Tong et al., Identification and Characterization of a pseudorabies virus isolated from a dead piglet born to vaccinated sow. Chinese Journal of Animal infectious diseases, 2013, 21(3):1-7; Yu et al., Pathogenic Pseudorabies Virus, China, 2012. Emerging infectious Diseases. 2014, 20(1):102-104; An et al., Pseudorabies virus variant in Bartha-K61-vaccinated pigs, China, Emerging infectious Diseases. 2013. 19(11): 1749-1755. There are no vaccines capable of solving the pseudorabies caused by variant strains of porcine pseudorabies virus in the prior art.
An effective method of preventing and controlling the pseudorabies caused by variant strains of porcine pseudorabies virus is inoculation with vaccines. The commercial vaccines to be developed may be inactivated vaccines, and also live vaccines prepared from attenuated strains. However, the cost of inactivated vaccines is relatively high, and usually the live vaccines are prepared by attenuating the strain via a deficiency of virulent genes by means of genetic engineering, resulting in the biosafety risk.